reduce-set.scm

;;; is 'lat' a set
(define set? (lambda (lat)
	(cond
		((null? lat) #t)
		(else 
			(cond
				((member? (cdr lat) (car lat)) #f)
				(else (set? (cdr lat))))))))

;;; is 'a' a member of 'lat'
(define member? (lambda (a lat)
	(cond 
		((null? lat) #f) 
		(else 
			(or 
				(eq? (car lat) a) 
				(member? a 
					(cdr lat)))))))

;;; is 'a' a subset of 'b'
;;; assumes 'a' and 'b' are both sets
(define subset? (lambda (a b)
	(cond
		((null? a) #t)
		((member? (car a) b)
			(subset? (cdr a) b))
		(else #f))))

;;; redefinition of subset?, using or's and and's instead of cond
(define subset? (lambda (a b)
	(or
		(null? a)
		(and
			(member? (car a) b)
			(subset? (cdr a) b)))))